a fairly common cam timing screw up

[grumpyvette]

FIRST GEN, SBC CLOYES ROLLER TIMING SET
https://www.summitracing.com/parts/clo-9-1100/overview/

MARK IV BBC CLOYES ROLLER TIMING SET 1965-90
https://www.summitracing.com/parts/clo-c-3024x/overview/

MARK VI BBC CLOYES ROLLER TIMING SET 1991-95
https://www.summitracing.com/parts/...-specific/engine-family/chevy-big-block-gen-v

when you go to install a cam, a fairly common new guy screw-up is if you index the upper and larger cam gear (0) index mark,on the smaller and lower crank gear 0 over the KEY-WAY slot,
I,D be amazed if it RUNS at all, installed indexed that way, but guys do occasionally screw up and index the upper larger cam gear to the 0 directly over the key-way slot on the smaller, lower , crank gear, which SHOULD in stead be in approximately in the 2 O'CLOCK location when the index marks ARE correctly aligned on both the crank at 12 o'clock and the cam gear at 6 o'clock
on some import timing sets the advanced 4 degrees is a tri-angle and the retarded 4 degrees is a rectangle, but its at times not marked well and guys get them installed wrong, Ive seen guys use the (O) on both lower and upper gears to align the cam on both sprockets but install the key way in the crank in the wrong slot, so the cams easily 30- 120 degrees out of phase, or use the KEYWAY (0) to INDEX THE UPPER CAM GEAR



the Cloyes 9-3649X3-5. Single roller with billet crank gear for the newer single roller BIG BLOCK CHEVY MARK V- and ESPECIALLY MARK VI with plastic timing cover engines that won,t allow use of the older thicker dual roller chain timing sets.
the timing chain picture above illustrates the off set from the KEY-WAY slot,to its related index mark that must be lined up with the cam gear above it, NOTICE THE (O) that LINES UP WITH THE CAM GEARS OFF TO THE LEFT NOT DIRECTLY ABOVE THE KEY WAY SLOT
YOU CAN AVOID POTENTIAL CONFUSION & PROBLEMS IF YOU TAKE THE TIME TOO, DEGREE THE CAMSHAFT IN, instead of relying on "dot-to-dot".

IF the lower crank gear index mark on the lower cam gear is correctly indexed (which its NOT yet rotated enough to do in the picture above)
the top cam gear is exactly twice the size of the lower crank gear,it rotates at exactly 1/2 speed or once for each TWO crank gear rotations ,if the cam gear and lower crank gear are correctly indexed the timing as they rotate will place the cam gear at EITHER 12 o'clock, or at 6 o'clock, exactly as the crank gear hits 12 o'clock on each rotation
notice in the lower picture the crank key way is at about the 2 o'clock position